Fortaleza de Nossa Senhora dos Prazeres, Portuguese colonial fortress on Mel Island, Paranaguá, Brazil.

Fortaleza de Nossa Senhora dos Prazeres is a defensive installation on Mel Island off Paranaguá, built from stone with thick walls and functional spaces for garrison troops. The structure follows the natural terrain of the island and shows the typical layout of coastal fortifications from the colonial period.

The fortress was built in the second half of the 18th century under Portuguese rule to protect the coast from unauthorized maritime traffic. It embodies Portuguese military strategy for securing its southern Brazilian possessions during this era.

The dedication to Nossa Senhora dos Prazeres, patroness of the Casa de Mateus, was chosen by the fortress's founder, D. Luís António de Sousa Botelho Mourão, fourth morgado de Mateus. The inauguration took place on 25 March 1769, and the fort is also known as Fortaleza da Barra. In the 1980s the site hosted a treasure hunt fuelled by the legend of Padre Thiago and by the discovery of a chest holding old papers and low-value coins.

Access is by boat from Paranaguá, with the crossing to the island taking some time and weather conditions worth considering. Sturdy footwear and sun protection are wise choices, as the terrain is uneven and the island offers little shade.

In 1850 the fort's commander, Captain Joaquim Ferreira Barbosa, mounted ten guns on improvised timber and stone platforms and drove off the British steam frigate HMS Cormorant, which had seized Brazilian ships in the port over the slave trade. The Cormorant fired back, hitting the slope of Morro da Baleia.